code: def _log_sub_sign(logx, logy):
      """Returns log(exp(logx)-exp(logy)) and its sign."""
      if logx > logy:
          s = True
          mag = logx + np.log(1 - np.exp(logy - logx))
      elif logx < logy:
          s = False
          mag = logy + np.log(1 - np.exp(logx - logy))
      else:
          s = True
          mag = -np.inf
  
      return s, mag
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import sys
  import numpy
  from scipy import special
  import six
label_desc: Use image node_id 3 for calling a global function with example usage: _log_sub_sign(logx, logy) and returns: s,  mag